The invention comprises a method for controlling quick setting of a pourable raw mixture having a filler material, water, calcium hydroxide, in some cases foam, and additionally cement, which consists at least partially of an aluminate capable of reacting with calcium hydroxide, in particular, an alumina cement, with an organic substance serving as a setting retarder for the aluminate, forming a complex and inhibiting the growth of calcium aluminum sulfate hydrate, in particular, hydroxycarboxylic acid.
A method for manufacturing concrete components is known from U.S. Pat. No. 4,102,962 in which a hydraulic cement is used which contains alumina cement (10-35% based on total cement), quick lime and/or calcium hydroxide (5-30% based upon the alumina cement), as well as a retarder in the form of an hydroxy-or ketocarboxylic acid or a salt thereof. Since a raw mixture made from this hydraulic cement immediately begins to set, large charges of the raw mixture to be continuously drawn upon cannot be produced, and instead the total charge must be poured immediately into a mold since no open holding times or pot-life are available. With this method, very limited quantities of lime are employed in order to avoid a very strong reaction already during the mixing of the raw mixture. Blank strength is achieved only after 20 minutes, and the demolded concrete must be allowed to stand for at least two hours to five days at a temperature less than 40.degree. C. in a humid atmosphere, after which autoclaving is undertaken.
A method of manufacturing cinder blocks for building materials made of a calcium silicate base is known from the U.S. Pat. No. 4,376,086. In this process, a pourable raw mixture is manufactured essentially out of a granular silicate-containing material such as quartz sand, lime, water, cement, and foam, whereby Portland cement together with a setting accelerator, and in some instances, a retarder and a correspondingly adjusted jet cement, respectively are used. This cement is used in order to achieve a satisfactory pot time for the raw mixture before it is poured into the mold during which practically no setting reactions take place. The latter reactions are caused initially in the mold substantially through the action of heat so that the formed blank exhibits a satisfactory strength for removal from a mold and transporting. The blank can then be hardened in an autoclave. This method requires, however, relatively large quantities of cement in order to acquire the necessary strength of the raw mixture, whereby it is difficult to control pot time and setting in a desired manner.
A jet cement is known from British Pat. No. 2,033,367. This cement contains Portland cement, calcium aluminate, calcium sulfate, an inorganic salt, a hydroxycarboxylic acid or a salt thereof, for instance sodium citrate, and when mixed with water posesses a pot time of approximately 20 minutes. However, if this type of quick setting cement is employed in a calcium hydroxide-rich environment, it sets in an uncontrolled manner and at an exceptionally fast rate since the calcium hydroxide reacts immediately with the calcium aluminate, as is also described in U.S. Pat. No. 4,102,962. The solidification regulators used would not prevent the fast setting. An appropriate solidification control would also not be possible with greater amounts of retarder additives, since these to be sure would halt the solification somewhat but would disturb rather severely subsequent hardness development. For the control of solidification and hardening of calcium hydroxide-rich systems, this quick setting cement is not suitable.
A cement is known from German Pat. No. 2,547,765 which contains an aluminua cement, calcium sulfate, an organic setting retarder, as well as a component releasing calcium hydroxide (hydrated) and some Portland cement. This cement is converted into ettringite on hydration and produces a quick setting cement. If this type of cement is employed in the presence of large quantities of free calcium hydroxide, an immediate setting takes place, so that the possibility of continuous control over the pot time and also the release therefrom by means of elevated temperatures are not possible. This system is controllable if there is no free calcium hydroxide available since the Portland cement does not possess any nominal value of freely available, calcium hydroxide. Portland cement contains at a maximum approximately 2% CaO which is strongly sintered due to high temperatures and is only slightly reactive. Additionally, the lime in mineral phases (for example, C.sub. 3S or C.sub. 2S) is firmly bonded and is set free as calcium hydroxide only in a period of hours.
It is known from French Pat. No. 2,233,295 on the one hand to manufacture a cement, mortar or concrete mixture, and on the other hand an effective material for fast solidification in the form of a powder or a suspension of calcium aluminate and an inorganic sulfate whereby the raw mixture yielded from the mixture of these products is immediately ready for working. The effective material can contain a hydroxycarboxylic acid retarder as well as an accelerator which can consist of at least some minimal quantities of calcium hydroxide. Apart from the minimal quantity of calcium hydroxide, nothing else would work in a calcium hydroxide-rich environment. The effective material should, if possible, not set for at least a half-hour; however, mixing with cement, mortar, or concrete should lead very swiftly to set. One should strive for a stiffening in a few minutes, for example, one to three minutes. By this means, however, the early strength on which the ettringit formation is based, is achieved slowly in the range of hours. In comparison, no controlled or long pot times, and activation through the application of heat on the total mixture can be strived for or obtained with early strength reached very rapidly.